Diabetes mellitus, often simply referred to as diabetes, is a chronic disease, which occurs when the pancreas does not produce enough insulin, or when the body cannot effectively use the insulin it produces. This leads to an increased concentration of glucose in the blood (hyperglycaemia). There are three main types of diabetes:                (1) Type 1 diabetes (previously known as insulin-dependent or childhood-onset diabetes), characterized by a lack of insulin production;        (2) Type 2 diabetes (formerly called non-insulin-dependent or adult-onset diabetes), which is caused by the body's ineffective use of insulin, and often results from excess body weight and physical inactivity; and        (3) Gestational diabetes, which is hyperglycemia that is first recognized during pregnancy.        
Normally, anti-diabetic drugs, which treat diabetes mellitus by lowering glucose levels in the blood, are administered orally and are thus also called oral hypoglycemic agents or oral antihyperglycemic agents. As of 2010, there are only two oral anti-diabetics in the World Health Organization Model List of Essential Medicines: Metformin and Glibenclamide [WHO Model List of Essential Medicines, 16th edition, World Health Organization, p. 24; December 2010].
Metformin, originally sold as Glucophage, is an oral antidiabetic drug in the biguanide class. It is the first-line drug of choice for the treatment of type 2 diabetes [Diabetes Care. 2009; 32 Suppl 1:S13-61]. Metformin is the only antidiabetic drug that has been conclusively shown to prevent the cardiovascular complications of diabetes. It helps reduce LDL cholesterol and triglyceride levels, and is not associated with weight gain. Metformin decreases hepatic glucose production, decreases intestinal absorption of glucose, and improves insulin sensitivity by increasing peripheral glucose uptake and utilization. With Metformin therapy, insulin secretion remains unchanged while fasting insulin levels and day-long plasma insulin response may actually decrease. However, Metformin is contraindicated in patients with renal disease or renal dysfunction. A long-term accumulation of Metformin may result in renal dysfunction.
It is desirable to develop new anti-diabetic drugs without contraindication.